Detection of clinically important β-lactamases in commensal Escherichia coli of human and swine origin in western China

摘要

Data correlating β-lactamases found in commensal Escherichia coli of human and animal origin are limited. In this study, 447 commensal E. coli isolates from the faeces of humans and swine (280 human isolates from four hospitals and 167 swine isolates from seven farms) were collected between September 2006 and January 2009 in western China. For extended-spectrum β-lactamase (ESBL)-producing and other cephalosporin-resistant isolates, the relevant β-lactamase genes (bla TEM, bla SHV, bla CTX-M-1/2/9 group, bla CMY-2 and bla KPC) were detected by PCR analysis. Of the 447 isolates tested, 120 (26.8 %) were confirmed as producing ESBL. Among these, 70 and 40 human isolates carried a member of the bla CTX-M-1 group (13 bla CTX-M-3, 21 bla CTX-M-15, four bla CTX-M-22, eight bla CTX-M-28, four bla CTX-M-36, 15 bla CTX-M-55 and five bla CTX-M-69) or bla SHV (14 bla SHV-2, seven bla SHV-5, ten bla SHV-12, five bla SHV-57 and four bla SHV-97),respectively, whilst six and four swine isolates carried a member of the bla CTX-M-1 group (one bla CTX-M-15 and five bla CTX-M-22) or bla SHV (three bla SHV-2 and one bla SHV-12), respectively. Furthermore, 59 human and swine isolates and seven human isolates carried bla CMY-2 and bla KPC, respectively. These findings indicate that the bla CTX-M-1 group, including the novel variant bla CTX-M-69, and bla SHV are the predominant ESBL genes in both humans and swine in western China, and bla CMY-2 is also common in both groups. The carriage rates of broad-spectrum β-lactamases among commensal E. coli was much lower in swine than in humans, suggesting that β-lactamase genes have not established themselves in animal ecosystems in western China.